Journal of a rose gardener 03/11/16
Dahlias are tender annuals, but can be overwintered indoors for re-planting the following year.
Once the foliage has been blackened by the first frost cut stems back to around 5cm from the base. Use a fork to lift the tubers. Be careful, as any damage caused can lead to rot in storage. Remove all loose soil from the tubers. Place them upside down in a cool position for at least 2 weeks to dry off.
Once dried off, label the tubers and store them in strong trays or boxes filled with dry soil or compost, leaving the stalks exposed. Keep the trays in a cold but frost free environment such as a greenhouse, shed, garage or cellar. Check periodically for rotting or drying out. Trim any rotted pieces to avoid the rot spreading.
If the tubers are drying out mist them lightly with water.
Begin to water from March onwards. Place in a lighter and warmer position.
Grow on and pot. Wait until the risk of frosts has passed and the soil has warmed before thinking of planting out again.